Compound fabrication process and apparatus

ABSTRACT

A miniature machine tool for micro-machining is capable of performing on a workpiece at least one conventional mechanical machining operation and another micro-machining operation such as electrochemical machining (ECM), electro deposit machining (EDM), micro-milling or micro-turning or micro-drilling. The machine tool includes a holder in which the workpiece is clamped during all successive machining operations so that the machining operations may be performed in succession without intervening reclamping of the workpiece. This increases dimensional accuracy when micro-machining high-precision components.

BACKGROUND OF THE INVENTION

[0001] a) Field of the Invention

[0002] This invention relates to a new or improved compound fabricationprocess and apparatus therefor, and in particular to the development ofa miniature machine tool for manufacture of micro, high precisioncomponents.

[0003] b) Description of the Prior Art

[0004] In general, conventional machine tools are used to manufacturemicro components. Usually the manufacture of such micro componentsrequires multiple machining processes such as micro Electrode DischargeMachining (EDM), micro Electro Chemical Machining (ECM), micro milling,micro turning and micro drilling. Therefore to manufacture a simple partmay entail use of more than one machine, depending on the geometry ofthe workpiece. For example to machine a micron sized hole in a workpieceone may have to first machine an electrode using turning, milling orother processes. The machined electrode will have to be placed in thespindle of an EDM machine to machine the micron-sized hole. During thisprocess, if the electrode is not properly aligned on the spindle withrespect to the workpiece there is a possibility of producing aninaccurate hole because of the set-up and machine errors. The prior artdoes not address the problem of combining multiple processes on a singleset-up, but is confined to simple single process machines such as thosedisclosed in U.S. Pat. No. 3,998,127, U.S. Pat. No. 5,439,431, U.S. Pat.No. 4,706,371, U.S. Pat. No. 4,646,422, U.S. Pat. No. 5,117,552.

[0005] The above mentioned references do not cover any method or meansfor combining conventional processes such as milling, turning, etc. withnon-conventional processes such as Electrode Discharge Machining orElectro Chemical Machining. Therefore when conventional andnon-conventional processes must be applied in succession there arisesthe possibility of inaccuracies in alignment of workpieces due to thefact that they have to be repositioned for conventional andnon-conventional machining. These problems are particularly acute in thecase of micro machining where the dimensional tolerances are very small.To minimize such inaccuracies, the present inventors have appreciatedthat it would be desirable to perform multiple manufacturing orfabrication processes in a single machine and thus avoid themanufacturing inaccuracies which are inherent in multi-stage processingoperations.

SUMMARY OF THE INVENTION

[0006] The objective of the invention is to provide an improvedfabrication process and apparatus through which multiple manufacturingsteps can be performed on a single platform without re-gripping of theworkpiece so that very significant improvements can achieved in terms ofthe dimensional accuracy of the workpiece being produced.

[0007] The invention provides a miniature machine tool for performing ona workpiece at least one conventional mechanical machining operation andat least another machining operation selected from electrochemicalmachining (ECM) and electro deposit machining (EDM); said machine toolincluding a holder in which said workpiece is clamped during saidmachining operations; wherein said machine tool is configured to performsaid machining operations in succession without intervening reclampingof the workpiece.

[0008] For example the machine can be a micro scale universal millingmachine in which various conventional forming operations such asturning, milling, drilling, shaping polishing and grinding can beperformed as is known, and wherein it is also possible to performnon-conventional machining processes such as Electro Discharge Machiningand Electro Chemical Machining. For example the machine tool can be usedto manufacture an electrode by known mechanical material removingprocesses and then used carry out a micro Electro Discharge Machiningoperation on the electrode. The equipment can also be used to carry outElectro Chemical Machining operations on milled or turned workpieces, orto perform electro discharge manufacturing on workpieces to improvesurface finish and accuracy. No machine in the prior art has thecapability to perform all the above listed steps on a workpiece.

[0009] A preferred apparatus for carrying out the invention comprises aminiature universal milling machine having a machine frame formed by agantry structure having two spaced vertical pillars connected at theirupper ends by a crosshead beam which supports a carriage on whichtooling such as a universal milling head can be adjusted horizontallyand vertically. A machine bed positioned in a lower part is arranged tobe adjustable in a horizontal plane and also vertically. The machine iscapable of supporting various driven spindles which can carry tools forperforming milling, drilling, grinding etc. operations.

[0010] The invention also provides a method of fabricating a workpiecein a miniature machine tool as described above, the method comprisingthe steps of: providing a workpiece blank and clamping said workpieceblank in said holder; performing a first conventional mechanicalmachining operation on said workpiece blank; and without re-gripping ofsaid workpiece blank performing a second machining operation thereon,said second machining operation being selected from ECM and EDM.

[0011] Typically the conventional mechanical machining operation will beperformed on the workpiece first followed by the second machiningoperation involving ECM or EDM, but in principle the order of theseoperations could be reversed.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0012] The invention will further be described, by way of example only,with reference to the accompanying drawings wherein:

[0013]FIG. 1 is a somewhat schematic front elevation of a miniaturemachine tool equipped for carrying out the method of the presentinvention;

[0014]FIG. 2 is a right side elevation of the machine tool of FIG. 1;

[0015]FIG. 3 is a front elevation of the machine tool illustrating adifferent tooling configuration;

[0016]FIG. 4 is a right side elevation corresponding to FIG. 3;

[0017]FIG. 5 illustrates three further tooling configurations which canbe used in the machine tool;

[0018]FIGS. 6, 7, 8 and 9 are schematic views illustrating mechanicalmachining operations that can be performed in the machine tool of FIGS.1 to 4; and

[0019]FIGS. 10, 11 and 12 are schematic views illustrating two-stagecompound machining operations that can be performed; and

[0020]FIGS. 13, 14 and 15 are views illustrating the manufacture of acomponent through a series of successive two-stage compound machiningoperations.

[0021]FIG. 16 illustrates the wire EDM attachment that can be used inthe machine tool of FIGS. 1 to 4.

[0022]FIGS. 17 and 18 illustrate the operation of the numerical controlsystem and how it is integrated to the machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] As shown in FIG. 1, a machine tool 10 in accordance with theinvention comprises a base frame 12 upon which is supported a pair ofbeds 14, 16 each of which is independently moveable under a controlleddrive system (not shown) to move in the fore-and-aft direction of themachine tool as indicated by the arrow 18 in FIG. 2. Each of the beds 14and 16 as will be more fully explained hereafter forms one component ofa machining station for carrying out operations on workpieces.

[0024] Rigidly attached to the base frame 12 are a pair of laterallyspaced vertical pillars 20 the upper ends of which are rigidly connectedto opposite ends of a horizontal crossbeam 22 which spans the width ofthe base frame as seen in FIG. 1.

[0025] In known manner, the crossbeam provides a horizontal guide formovement of a carriage 24 thereon, this carriage in turn providingguidance for vertical movement of a linear slide 26 therein. The linearslide in turn provides a mounting for various tooling or work grippingcomponents such as the indexing head 28 shown in FIGS. 1 and 2.

[0026] The basic machine tool configuration described above is notdisclosed in any detail since it is well understood by those skilled inthe art. It will be seen that the indexing head 28 accommodates fourreplaceable tooling or gripper sets 30 extending at angular intervals of90° thereon.

[0027] In known manner the machine tool includes drive means selectivelyengageable to apply a powered drive for rotation of a selected one ofthe tooling sets/grippers 30 when it is desired to perform a mechanicalmachining process on a workpiece. As is known in such machine tools, themechanical machining process can be selected from drilling, milling,shaping, turning, grinding, and polishing.

[0028] In the machine tool as illustrated in FIG. 3, the indexing head28 is replaced by a drill head 32, and depending upon the requirementsit could equally well be replaced by the components shown in FIG. 5namely (a) a milling head 34, (b) a polishing head 36, or (c) a grindinghead 38.

[0029]FIG. 1 shows the machine tool 10 configured to perform insuccession a turning operation and an EDM or ECM operation. In thisset-up the downwardly directed tool holder 30 is configured to grip theworkpiece W in a power driven rotatable holder 40 to be machined byturning, metal removeable being performed by a cutting tool 41 held in atool mount 42 carried on the bed 16. By suitable manipulation of therelative positions of the workpiece W and the tool mount 42, a requiredturning operation can be performed on the workpiece W as it is rotatedby the holder 40. Thereafter, while still engaged within the holder 40,the workpiece W can be transferred to the location of a tank 44 (carriedon the left hand bed 14 as seen in FIG. 1) for the performance thereinof an EDM or an ECM operation. Separate tanks are used for EDM and ECMoperations. For an EDM operation, the tank 44 is filled with dielectricmedium whereas for ECM operations the ECM tank 44 will be filled withelectrolyte. The use of two different delivery systems avoids thepossibility of cross contamination.

[0030]FIG. 3 shows the machine tool 10 set up to perform a micro millingoperation on the workpiece. The workpiece is held in a gripper 35 thatis mounted on the linear slide 26, the workpiece then being brought intothe vicinity of the milling tool 37 held in the milling head, therelative positions of the tool 37 and the workpiece W being manipulatedas the tool is rotated to effect the desired milling operation. This isgraphically illustrated in FIG. 7.

[0031]FIG. 6 shows an alternative machining operation wherein therotating spindle 46 carries the workpiece for machining by the tool 41.

[0032]FIG. 8 shows the rotating spindle 46 carrying a grinding wheel 50for performing a grinding operation on the stationary workpiece W.

[0033]FIG. 9 shows the rotating spindle 46 carrying a polishing tool 52for performing a polishing operation on the workpiece W.

[0034]FIG. 10 illustrates two operations to effect hybrid machining forforming micro holes. In FIG. 10a the workpiece W held in the drivenspindle 46 is machined by the turning tool 41 to produce an electrode54. In a subsequent step as indicated in FIG. 10b the electrode 54 isthen used in a micro EDM operation to produce a hole in a workpiece W.

[0035]FIG. 11 illustrates a milling tool 48 held in the driven spindle46 and manipulate to cut a desired profile in an electrode 56. Theelectrode is then inverted as shown in FIG. 11b and used in an EDMprocess to shape the workpiece W.

[0036] As shown in FIG. 12a the spindle 46 first holds an electrode 58used in an EDM process to act upon a workpiece W. In a subsequentoperation as shown in FIG. 12b the workpiece is further processed in anECM operation by an electrode 60.

[0037] The hybrid machining operations described in the foregoing inrelation to the apparatus shown in the drawings provide the mainadvantage that they enable the machining of micro components of greataccuracy without changing the machine set up. For example an electrodemachined by micro turning or micro milling can be further processed bymicro ECM (electrical chemical machining) to improve its surfacesmoothness and dimensional accuracy, and this same electrode can then beused in a micro EDM operation to reconfigure functional components. Inthese means errors which could otherwise arise due to clamping or set uptolerances can be eliminated.

[0038] It will be appreciated that various other hybrid micro machiningoperations can be performed by combining selected operations to ensurethat workpieces are produced with improved dimensional accuracy. Forexamples FIGS. 13, 14 and 15 illustrate successive steps in a hybridmachining process for producing in a workpiece W a mould cavityconfiguration as shown in the right hand view of FIG. 15. Initially, asshown in FIG. 13 a turning tool 41 is employed to produce the desireddimensions of an electrode 64 that is rotated in the driven spindle 46.Thereafter this electrode 64 is employed to produce in the workpiece W apreliminary cavity 61 a corresponding to the profile of the electrode.

[0039] Subsequently, as shown in FIG. 14, without removing the electrode64 from the spindle 46, the lower end of the electrode is rounded as at64 a by the turning tool 41, where after the spindle 46 is used totransfer the modified electrode to produce by an EDM process roundeddepressions 65 providing a modified recess 61 b in the workpiece W.

[0040] In a further stage as shown in FIG. 15 the turning tool 41 isagain used to reconfigure the electrode 64 to provide a small diameterextension 67. This extension 67 is then used as shown in the right handpart of FIG. 15 to produce by an ECM process a central hole through theworkpiece W.

[0041] As depicted in FIG. 16, a portable wire EDM 100 can be attachedto the spindle 46. The wire EDM 100 is driven by a motor which makes thewire move around. The attachment can be tilted to any angle in order toproduce slots of any angle. One such arrangement to produce a slot usingthe wire EDM attachment is shown in FIG. 16.

[0042] Movements of the various components of the machine tool aredriven under a program provided by a central processing unit connectedto a numerically controlled system which can be designed to carry outvarious hybrid machining processes in predetermined combinations. FIGS.17 and 18 are flow-charts showing the system logic for numericallycontrolled machining.

[0043] Briefly stated, the machine tool and the processes describedabove deliver at least the following advantages:

[0044] 1. By virtue of the gantry structure of the micro machine toolthe stability of the various components in the machine is enhanced andthe dimensional accuracy of resulting workpieces is therefore improved.

[0045] 2. The described system provides the capability to machine microcomponents using conventional and non-conventional hybrid machiningprocesses which can include two or more of the following: micro milling;micro turning; micro EDM; micro ECM; micro polishing; and microgrinding, all performed on the same machine tool.

[0046] 3. The system provides the capability of manufacturingnon-cylindrical EDM and/or ECM electrodes in the single tool.

[0047] 4. The system provides the capability of using EDM or ECMelectrodes produced therein without changing the machine set up.

[0048] 5. The system provides the capability of performing wire cut EDMusing a portable attachment.

What is claimed is:
 1. A miniature machine tool for performing on aworkpiece at least one conventional mechanical machining operation andat least another machining operation selected from electrochemicalmachining (ECM) and electro deposit machining (EDM); said machine toolincluding a gripper in which said workpiece is clamped during saidmachining operations; wherein said machine tool is configured to performsaid machining operations in succession without intervening reclampingof the workpiece.
 2. A miniature machine tool as claimed in claim 1comprising: a rigid machine frame having a horizontally oriented bed, apillar structure rigidly attached to said bed and extending verticallytherefrom, and a gantry supported on said pillar structure and extendinghorizontally; a first carriage guided for movement on said gantry in afirst horizontal direction; a second carriage carried by said firstcarriage and guided thereon for movement vertically; a third carriagesupported by said second carriage and configured to support a firstelement selected from a tool and a workpiece; a fourth carriage mountedon said machine frame bed and guided for movement thereon in ahorizontal direction that is perpendicular to said first horizontaldirection; said fourth carriage being configured to support a secondelement selected from a tool and a workpiece; a fifth carriage mountedon said machine frame bed and guided for movement thereon in ahorizontal direction that is perpendicular to said first horizontaldirection; positioning drive means connected to each said carriage toeffect changes in the position of the associated carriage; saidworkpiece gripper being carried in one of said third, fourth and fifthcarriages; a tool holder carried in a second of said third, fourth andfifth carriages; a machining element carried in the remaining one ofsaid third, fourth and fifth carriages; and a machining drive connectedand selectively operable to effect relative movement between said toolholder and said machining element with respect to a workpiece carried insaid gripper to effect said machining operations on said workpiece in atleast first and second locations in said machine tool.
 3. A miniaturemachine tool as claimed in claim 2 wherein said one machining operationis selected from micro milling, micro turning, micro grinding and micropolishing.
 4. A miniature machine tool as claimed in claim 2 whereinsaid pillar structure comprises a pair of laterally spaced verticalpillars, each said pillar having a lower end that is rigidly connectedto said bed and an upper end; said gantry comprising a horizontal beamhaving opposite ends which are rigidly affixed to the upper ends of saidrespective pillars; said machine including powered drive systemsconnected to each of said movable carriages to effect preciselycontrolled movements of said carriages; said powered drives beingoperated under control of a central processor unit which is programmableto effect a predetermined sequence of movements in performing theselected machining operations on a workpiece.
 5. A miniature machinetool as claimed in claim 1 and further comprising a portable attachmentthat is engageable with said machine tool and that is configured toperform wire cut EDM.
 6. A miniature machine tool as claimed in claim 2in combination with one or more detachable spindles for micro milling;micro drilling; micro grinding; micro polishing; micro EDM; wire cutmicro EDM; and ECM.
 7. A miniature machine tool as claimed in claim 1configured to perform said another machining operation after completionof said one conventional machining operation.
 8. A method of fabricatinga workpiece comprising: providing a miniature machine tool as claimed inclaim 1; providing a workpiece blank and clamping said workpiece blankin said gripper; performing a first conventional mechanical machiningoperation on said workpiece blank; and without re-gripping of saidworkpiece blank performing a second machining operation thereon, saidsecond machining operation being selected from ECM and EDM.
 9. A methodas claimed in claim 7 wherein said first machining operation is selectedfrom drilling, milling, turning, grinding, and polishing.
 10. A methodas claimed in claim 8 wherein said second machining operation is EDMusing a portable attachment on said miniature machine tool.
 11. Acompound fabrication process comprising: providing a machine having afirst station that includes tooling for mechanical removal of materialfrom a workpiece and a second station that includes processing equipmentfor creating non-mechanical dimensional change in said workpiece;locating said workpiece relative to one of said equipment stations bygripping said workpiece in a clamping structure; and processing saidworkpiece in said two stations successively, with transfer of saidworkpiece between stations without regripping of said workpiece withrespect to said clamping structure.
 12. A compound fabrication processas claimed in claim 11 wherein said tooling at said first station isadapted to effect removal of material from said workpiece by a processselected from turning, milling, drilling, grinding, and polishing.
 13. Acompound fabrication process as claimed in claim 11 wherein saidprocessing equipment at said second station is selected from electrodedischarge machining (EDM) equipment and electrochemical machining (ECM)equipment.
 14. A compound fabrication process as claimed in claim 11 forprocessing a metal workpiece wherein the workpiece is first processed insaid first station using tooling selected from: equipment for turning,milling, drilling, grinding, and polishing; and is then processed atsaid second station by processing equipment selected from electrodedischarge machining equipment and electrochemical machining equipment.15. Apparatus for performing compound fabrication steps on a workpiece,comprising: a processing machine having first and second stations forperforming successive operations on said workpiece; one said stationincluding tooling for mechanical removal of material from saidworkpiece; the other said station including processing equipment forcreating dimensional change in said workpiece; said apparatus includinga clamping structure for gripping said workpiece and indexing equipmentfor movement of the clamped workpiece between said stations such thatprocessing of the workpiece at both stations can be performed withoutre-gripping of the workpiece in said clamping structure.